This invention relates to an engine for models having a fuel injector and throttle valve, and particularly relates to a programmable engine for models which determines the driving timing of the fuel injector and the quantity of fuel injection depending on the opening of the throttle valve and driving stroke of the engine.
Conventionally, for glow engines of two-cycle or four-cycle which have been known as an engine for models, a carburetor 100 having the structure as shown in FIG. 8 have been used as the means for controlling the feeding rate of fuel to a combustion chamber of an engine.
In the housing 101 of the carburetor 100, a valve body 102 having the shape like a cylinder is provided rotatably around the axis line of the valve body 102 itself. Pipe conduit 101a and 101b extend vertically through the housing 101, and air is supplied from the upper pipe conduit 101a. A passage 102a extends through the valve body 102, and the passage is communicated to the pipe conduits 101a and 101b of the housing 101 with the opening depending on the rotation angle of the valve body 102. An operating arm 103 is connected to a portion of the valve body 102 which projects beyond the one end of the housing 101. An operating part of a servo mechanism not shown in the figure is connected to the operation arm 103, and the servo mechanism rotates the valve body 102 in the housing 101. A needle 104 is fixed to the valve body 102 with a screw, and the projection extending into the valve body 102 is adjustable by turning the needle 104.
A fuel control needle valve 105 is built-in at the other end of the housing 101. The needle valve 105 has a tube 106 and a needle 107 provided in the tube 106. The needle 107 is fixed to the tube 106 with a screw, and the needle 107 is moved in reverse in the tube 106 by turning a knob 108 provided at the base of the needle and the tip opening of the tube 106 can be adjusted. The tip of the needle 104 provided to the valve body 102 is facing to the opening of the tip of the tube 106 of the needle valve 105.
Fuel fed to the needle valve 105 is injected from the clearance between the tip of the tube 106 and the needle 107 to the internal, mixed with air supplied in the valve body 102, and fed to an engine. Because the flow rate of fuel can be adjusted by turning the knob of the needle valve 107, the flow rate of fuel (or air-fuel ratio) can be previously set so that the engine rotates at the maximum rotation speed. The servo mechanism rotates the valve body 102 to adjust air flow rate into the valve body 102, and controls the flow rate of fuel fed to the engine.
According to the carburetor 100, when the engine is accelerated rapidly from the low rotation condition such as idling, a lot of air is fed in the valve body, but the supply of fuel can not follow the supply of air, and the balance of air-fuel ratio is unbalanced. The rotation of the engine increases not smoothly and increases slowly, and can be stopped in the bad case. As a whole, the response is not speedy, the transition from the low rotation speed to high rotation speed or the high rotation speed to low rotation speed requires a long time, it is a disadvantage of the conventional engines. Further, in the case that an engine for models is mounted on a radio control model plane, fuel is fed not adequately to the carburetor due to the adverse effect of centrifugal force caused by flying motion of the model plane, the inadequate feeding of fuel causes the malfunction of the engine.
It is an object of the present invention to provide a fuel injector which is capable of injecting adequate quantity of fuel at adequate timing stably and maintaining the air-fuel balance, capable of deriving the stable and high performance of the engine for models, and capable of speedy response of the engine which is used usually under the severe condition as an engine for models mounted on a radio control model plane for acrobatic flying such as loop flying.